1. Field of the Invention
The present invention relates to a method for epitaxially growing a single crystalline silicon thin film on a single crystalline insulating substance such as a single crystalline sapphire substrate and a single crystalline spinel film.
2. Description of the Prior Art
In general, the SOS (Silicon on Sapphire) techology has been used as a method for achieving the high integration, high-speed and reduction of electric power consumption of an integrated circuit. This is a method for epitaxially growing a single crystalline silicon film on a single crystalline sapphire substrate. This SOS technology has adantages in that, for example, the separation of elements which are integrally formed in an epitaxial film can be easily carried out by etching and the like, and the problem of latch-up incidental to an integrated circuit on a usual silicon substrate can be prevented.
The vapor-phase growth method by the thermal decomposition of monosilane (SiH.sub.4) has been frequently used for epitaxially growing a single crystalline silicon film on a single crystalline sapphire substrate. However, this vaporphase growth method has shown disadvantages in that the growing temperature is high to an extent of 950.degree. C. or more the there is a great difference of thermal expansion coefficient between sapphire and silicon, so that crystal defects are introduced into the epitaxial film of grown single crystalling silicon to increase a defect-density and aluminum atoms and oxygen atoms of the sapphire substrate are autodiffused into the epitaxial silicon film, whereby a highquality epitaxial silicon film is difficult to obtain. Accordingly, a semiconductor device formed in an epitaxial single crystalline silicon film formed by such vapor-phase growth method has shown a disadvantage in that sufficiently satisfactory characteristics can not be achieved. In view of such problems, the epitaxial single crystalline silicon film has been intended to grow at lower temperature. Such low-temperature growing method includes the low-pressure vapor-phase growth method and the molecular beam epitaxy method (MBE method). A method of producing a SOS film by the MBE method, by which the above described disadvantages can be eliminated, has been reported by Dr. J. C. Bean of the Bell Laboratory in Applied Physics Letters 36 (9), 1 May, 1980, p. 741-743 as one example of the latter.
In this report a method for obtaining the SOS structure, in which a sapphire substrate with a (1102) plane chemico-mechanically mirror-finished as a main plane is spattered with argon ions (Ar.sup.+) at a temperature thereof of 1,000.degree. C. in a superhigh vacuum of 10.sup.-11 Torr or subjected to the flash annealing for a short time at high temperature thereof of 1,400.degree. C. to clean a surface thereof and then the sapphire substrate is subjected to the MBE with keeping lower temperature thereof ranging from 600.degree. to 850.degree. C. to epitaxially grow a single crystalline silicon film, has been reported.
However, this method has the following three problems:
Since the sapphire substrate is heated at high temperature of 1,000.degree. C. or more when it is cleaned,
(1) Defects, such as a warp and slip lines, are apt to be produced at the sapphire substrate. PA2 (2) There is the possibility that the degree of vacuum is reduced by a gas generated from a wall surface of the growing chamber, a heater or jigs of the sapphire substrate, and simultaneously, the sapphire substrate is recontaminated with such a gas generated. This leads to the deterioration of the epitaxially grown single crystalline silicon film in quality together with the problem (1). PA2 (3) measures for improving the heat-resistance and the durability of the jigs of the substrate and the like become necessary, whereby the apparatus becomes complicated and expensive.